Myosin

chemical compound

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The structure of striated muscle

Striated muscle tissue, such as the tissue of the human biceps muscle, consists of long, fine fibres, each of which is in effect a bundle of finer myofibrils. Within each myofibril are filaments of the proteins myosin and actin; these filaments slide past one another as the muscle contracts and expands. On each myofibril, regularly occurring dark bands, called Z lines, can be seen where actin and myosin filaments overlap. The region between two Z lines is called a sarcomere; sarcomeres can be considered the primary structural and functional unit of muscle tissue.

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The structure of actin and myosin filaments.

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major reference

The main constituent of the thick filaments is
myosin. Each thick filament is composed of about 250 molecules of
myosin. Myosin has two important roles: a structural one, as the building block for the thick filaments, and a functional one, as the catalyst of the breakdown of ATP during contraction and in its interaction with actin as part of the force generator of muscle. The individual
myosin...

occurrence in meat

...colour changes during cooking correspond to structural changes taking place in the meat. These structural changes are due to the effects of heat on collagen (connective tissue protein) and actin and
myosin (myofibrillar proteins). In the temperature range between 50 and 71 °C (122 to 160 °F) connective tissue in the meat begins to shrink. Further heating to temperatures above 71 °C...

role in

cardiovascular system

...known as myofibrils that house highly organized contractile units called sarcomeres. The mechanical function arising from sarcomeres is produced by specific contractile proteins known as actin and
myosin (or thin and thick filaments, respectively). The sarcomere, found between two Z lines (or Z discs) in a muscle fibre, contains two populations of actin filaments that project from opposite Z...

cytoplasmic streaming

...organelles and other molecules through the cytoplasm. Motor proteins often consist of actin filaments, long protein fibres aligned in rows parallel to the streaming just inside the cell membrane. Myosin molecules attached to cellular organelles move along the actin fibres, towing the organelles and sweeping other cytoplasmic contents in the same direction.

muscle contraction

...and utilization—e.g., movement, generation of electricity, transport of materials across cell membranes, and production of light by cells. Soon it was discovered that a muscle protein called
myosin acts as an enzyme (organic catalyst) by liberating the energy stored in ATP and that ATP in turn can modify the physical properties of
myosin molecules. It was also shown that a muscle fibre...

...extensively studied in muscle cells. In muscle cells, the actin filaments are organized into regular arrays that are complementary with a set of thicker filaments formed from a second protein called
myosin. These two proteins create the force responsible for muscle contraction. When the signal to contract is sent along a nerve to the muscle, the actin and
myosin are activated. Myosin works as a...

...cell cytoplasm) from the extracellular surroundings. Within the sarcoplasm of each individual muscle fibre are approximately 1,000 to 2,000 myofibrils. Composed of the contractile proteins actin and
myosin, the myofibrils represent the smallest units of contraction in living muscle.

pseudopodial locomotion

Although amoeboid motion is characteristic of the amoeba, a unicellular protozoan, it is also found in nonmuscle cells of multicellular organisms. These cells contain
myosin and actin, which differ in some aspects of their structure from the corresponding proteins in muscles because of variations in the genes that encode them.

...The basic locomotory organelle is the pseudopodium. The way in which movement is effected can vary slightly among groups but generally involves the polymerization of cytoskeletal proteins (actin and
myosin) at the leading edge of the pseudopod, followed by the flow of cytoplasmic material into the vacancy produced through the polymerization process. The flow of cytoplasm provides the momentum...

smooth muscle

...cells 50 to 250 μm in length by 5 to 10 μm in diameter. These cells possess a single, central nucleus. Surrounding the nucleus and throughout most of the cytoplasm are the thick (
myosin) and thin (actin) filaments. Tiny projections that originate from the
myosin filament are believed to be cross bridges. The ratio of actin to
myosin filaments (approximately 12 to 1) is twice...

type of contractile protein

Myosin, which can be removed from fresh muscle by adding it to a chilled solution of dilute potassium chloride and sodium bicarbonate, is insoluble in water. Myosin, solutions of which are highly viscous, consists of an elongated—probably double-stranded—peptide chain, which is coiled at both ends in such a way that a terminal globule is formed. The length of the molecule is...

work of Huxley

...sliding-filament theory of muscle contraction. An explanation for the conversion of chemical energy to mechanical energy on the molecular level, the theory states that two muscle proteins, actin and
myosin, arranged in partially overlapping filaments, slide past each other through the activity of the energy-rich compound adenosine triphosphate (ATP), causing muscle contraction.